1. Field of the Invention
This invention relates generally to disk drive systems and more specifically to a disk drive system having skewed data tracks.
2. Description of the Prior Art
Floppy disks are flexible magnetic media on which data may be recorded as magnetic pulses. The disks are inserted in disk drives for reading and writing in connection with computer systems.
Software manufacturers and producers duplicate a single software program onto disks for mass distribution. In the duplication production process, disk drives are connected to an industrial floppy disk copier which can write the same program onto several different disks in several different disk drives at the same time.
A problem with disk drives in computers as well as industrial disk copiers is that a relatively long time is required to write an entire disk. For example, in a standard double-sided floppy disk drive (48 TPI) the time required to duplicate a disk is approximately forty seconds. On the first revolution of the disk, the drive writes side zero of a first track. A typical revolution takes two hundred milliseconds. The disks rotate at three hundred revolutions per minute. On the second revolution, the drive verifies the data just written on side zero of that track. On the third revolution, the drive writes side one of the first track. On the fourth revolution, the drive verifies the data just written on side one on the first track. After the fourth revolution, the drive immediately steps the transducer head to the next track. However, a time period must pass before writing can begin to allow the head to settle into a stable position after the movement. At this point, the head has already passed the index position (i.e., the physical reference position which is used to locate the beginning of the track writing operation) and the head must complete a fifth revolution before writing can begin on the next index position. Each disk has an index hole for detection by an index sensor which in turn can generate an index pulse. This index pulse is then used by the disk drive as a signal that the disk is in position for commencing the write operation.
Thus, five complete revolutions of the disk are needed to write a single track on each side of a double-sided disk. Although the time delays for each of these revolutions are small, the total delay for writing the entire disk is substantial. Accordingly, a need exists to improve the speed of the disk writing operation.